ZURICH, July 2 (Reuters) - Swiss drugmaker Roche said on Monday that a trial showed its immunotherapy Tecentriq plus the chemotherapy Abraxane significantly reduced the risk of disease worsening or death in people with metastatic triple negative breast cancer.

The company, citing its IMpassion130 study, said it also recorded an encouraging overall survival benefit for the PD-L1 positive population, whose tumours express a protein that help them evade immune system detection, at interim analysis.

The Basel-based company called this the first Phase III immunotherapy study in first-line metastatic triple negative breast cancer to demonstrate a statistically significant improvement in progression-free survival in key patient groups, including the conservative intention-to-treat population.

Patients with triple-negative breast cancer test negative for hormone receptors or HER2, meaning their tumours do not respond to hormone therapy or to therapies like Roche's $7 billion-per-year blockbuster Herceptin.

As a result, there is significant interest in finding new, better ways to tackle this form of the disease.

"Highly encouraged by these results, we plan to submit to health authorities globally with the aim of bringing this combination to people with triple negative breast cancer as soon as possible," Roche Chief Medical Officer Sandra Horning said in a statement.

About 12 percent of breast cancers diagnosed in the United States are triple negative, according to the American Cancer Society. (Reporting by John Miller; Editing by Himani Sarkar)